Patent GB-731061-A (GB)
Title: Processes for making carboxylic acids
IPC: C07C29/60
Filed: 1951-08-08
Abstract: Monobasic and dibasic scission derivatives of aliphatic polyhydroxy carboxylic acid compounds having from 11 to 22 carbon atoms are prepared by a process comprising maintaining sodium hydroxide, potassium hydroxide or lithium hydroxide at an elevated temperature and gradually adding the selected aliphatic polyhydroxy carboxylic acid compound.  The term "polyhydroxy acid compound" includes any aliphatic polyhydroxy acid having from 11 to 22 carbon atoms, e.g. 9, 10-dihydroxy stearic acid, 10,11 - dihydroxyundecanoic acid, trihydroxystearic acid, tetrahydroxy stearic acid and 13,14-dihydroxy behenic acid and all of the position isomers of the above compounds as well as their functional saponifiable derivatives, e.g. the esters, amides, alkali metal salts and epoxy compounds which react with caustic to form aliphatic polyhydroxy carboxylic acids having from 11 to 22 carbon atoms.  Generally the dry hydroxide is maintained at a temperature between the melting-point and the temperature just p  below that at which the products decompose.  Most of the oxygen or air is excluded from the reaction vessel and the reaction will proceed in an atmosphere free of oxygen, e.g. of carbon dioxide or nitrogen.  On completion of the reaction the reaction mass is cooled, diluted and acidulated with a mineral acid.  Separated oil layers are washed and distilled, steam being introduced if desired, to collect the monobasic acid.  The water layers are evaporated and cooled to crystallize the dibasic acid.  The reaction may be carried out in the presence of water if a pressure vessel is used and continuous operation may be employed.  In a diagram of apparatus which may be used (not shown) a closed kettle, surrounded by a jacket containing a heating fluid, is provided with agitators, injectors for inert gas and hydroxy compound and an inert gas vent.  If products are distilled off distillation and separation equipment are connected through the latter.  In examples: 9,10-Dihydroxystearic acid is added dropwise to preheated liquid sodium hydroxide under carbon dioxide, the reaction mass is cooled, diluted with water and acidulated, the oil layer containing pelargonic acid is separated and azelaic acid is obtained from the aqueous layer (I) and (IV); a mixed dibasic acid and an oil layer containing C8 to C10 monobasic acids are similarly obtained from 80 per cent dihydroxy stearic acid containing amongst other isomers the 9,10-dihydroxy acid, using sodium hydroxide under nitrogen (II); 9,10-dihydroxy-stearic acid (low melting form) is similarly converted to pelargonic acid and azelaic acid, steam distillation being employed in isolating the former (V); 9,10,12-trihydroxystearic acid is similarly converted apparently to caproic acid mixed with pelargonic acid and a mixture of sebacic and azelaic acids (VI); sebacic acid is similarly obtained from 10,11-dihydroxyundecanoic acid (VII); pelargonic acid containing n-nonyl alcohol and crystals of acid number 546 are similarly obtained from 9,10-dihydroxystearic acid (VIII); brassylic acid containing azelaic acid and pelargonic acid are similarly obtained from 13,14-dihydroxybehenic acid (low melting form) (IX); methyl 9,10-dihydroxy stearate is heated under reflux with aqueous potassium hydroxide and high-boiling mineral oil, the mass is cooled and diluted and the mineral oil is separated, the remaining mass is acidulated with sulphuric acid and the oil layer formed is extracted with boiling water, the extract is combined with the original water layer and azelaic acid is separated. Pelargonic acid containing small amounts of n-nonyl alcohol is obtained by steam-distillation of the oil layer.